The emerging picture of the mitochondrial protein import complexes of Amoebozoa supergroup

Małgorzata Wojtkowska,Dorota Buczek,Wojciech Makałowski,Yutaka Suzuki,Hanna Kmita,Victoria Shabardina

doi:10.1186/s12864-017-4383-1

Małgorzata Wojtkowska, Dorota Buczek + Show 4 more

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https://doi.org/10.1186/s12864-017-4383-1

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Abstract

BackgroundThe existence of mitochondria-related organelles (MROs) is proposed for eukaryotic organisms. The Amoebozoa includes some organisms that are known to have mitosomes but also organisms that have aerobic mitochondria. However, the mitochondrial protein apparatus of this supergroup remains largely unsampled, except for the mitochondrial outer membrane import complexes studied recently. Therefore, in this study we investigated the mitochondrial inner membrane and intermembrane space complexes, using the available genome and transcriptome sequences.ResultsWhen compared with the canonical cognate complexes described for the yeast Saccharomyces cerevisiae, amoebozoans with aerobic mitochondria, display lower differences in the number of subunits predicted for these complexes than the mitochondrial outer membrane complexes, although the predicted subunits appear to display different levels of diversity in regard to phylogenetic position and isoform numbers. For the putative mitosome-bearing amoebozoans, the number of predicted subunits suggests the complex elimination distinctly more pronounced than in the case of the outer membrane ones.ConclusionThe results concern the problem of mitochondrial and mitosome protein import machinery structural variability and the reduction of their complexity within the currently defined supergroup of Amoebozoa. This results are crucial for better understanding of the Amoebozoa taxa of both biomedical and evolutionary importance.

Highlights

The existence of mitochondria-related organelles (MROs) is proposed for eukaryotic organisms
We investigated the presence of genes encoding subunits of the mitochondrial protein import complexes located in the intermembrane space and inner membrane using available genome and transcriptome sequences
The reason is that we noticed some differences between the transcriptome datasets reflected in amino acid sequences of proteins predicted for the mitochondrial outer membrane [14]

Summary

Introduction

The existence of mitochondria-related organelles (MROs) is proposed for eukaryotic organisms. The mitochondrial protein apparatus of this supergroup remains largely unsampled, except for the mitochondrial outer membrane import complexes studied recently. Studies of the mitochondrial protein import machinery have revealed that the machinery consists of complexes located in all mitochondrial compartments and have provided information about their organization, function, and interplay. The S. cerevisiae protein import machinery, schematically shown, is defined as a canon and applied as a reference model in studies of the machinery of other eukaryotic organisms, including plants and animals [7,8,9]. The TOM (translocase of the outer membrane), TOB/SAM (topogenesis of the mitochondrial outer membrane β-barrel proteins/sorting and assembly machinery) and MIM (mitochondrial import machinery) complexes are located in the outer membrane. The MIA complex is responsible for the import of small intermembrane space proteins with the multiple cysteine residues due to the thiol-disulfide exchange, whereas small Tims associate with the TOB/SAM and TIM22 complexes to protect precursor proteins from misfolding in the intermembrane space

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